Multiple sclerosis (MS) is a devastating inflammatory disease of the central nervous system (CNS) in which myelin and oligodendrocytes are depleted from large areas of white matter. The nature of the immunologic attack is not well understood and the relative contributions of T and B cells are debated. Recent work suggests that the process of myelin destruction in MS may vary among lesions. This proposal centers on the hypothesis that effector mechanisms leading to demyelination in MS lesions are heterogeneous. Four approaches will be investigated. The first will examine MS lesions at different stages of development for the involvement of antibodies in myelin destruction with a recently-developed technique using conjugates of known peptides of myelin antigens coupled to gold to localize autoantibodies in situ in MS lesions. With a similar immunocytochemical technology, cytokine profiles in MS lesions will be evaluated. Whether cytokines localize to the same or different regions as antibodies in the lesion or are associated with particular stages of lesion development will be studied. The second area will study by immunocytochemistry, ISH, RPA and immunoblotting, the relative roles of immunoglobulin (Ig) and cytokines in a murine model of experimental autoimmune encephalomyelitis (EAE), in which a gene critical for B cell development (uMT) has been deleted and in which it has been shown that despite the lack of antibody, the mice develop CNS lesions similar to wild-type controls. This suggests either that heterogeneity in myelin destruction exists, that Ig is not needed for demyelination, or that the mouse (or the C57BL/6 strain) is different from other species (or strains). The third aim follows on using similar technologies to examine EAE in a susceptible strain, SJL, induced by active and by adoptive sensitization. The prediction is that antibody involvement will be the effector mechanism after active sensitization and that cytokines will be more prominent in the adoptive transfer model. The final area to be examined relates to mechanisms underlying the oligodendroglial survival response around active lesions in MS where remyelination is commonly seen. For this, localization and expression of molecules of the NFkappaB, c-Jun and Bcl-2 cascades will be investigated in well-characterized MS lesions. It is hypothesized that as with patterns of demyelination, heterogeneity also occurs in the oligodendrocyte response in MS. Understanding the variability in the above mechanisms in MS might lead to better monitoring of the disease and the patient, and should provide data readily translatable to the clinic.